文档介绍：Table of Contents
Chapter 12 1
Chapter 13 145
Chapter 14 242
Chapter 15 302
Chapter 16 396
Chapter 17 504
Chapter 18 591
Chapter 19 632
Chapter 20 666
Chapter 21 714
Chapter 22 786
Engineering Mechanics - Dynamics Chapter 12
Problem 12-1
A truck traveling along a straight road at speed v1, increases its speed to v2 in time t. If its
acceleration is constant, determine the distance traveled.
Given:
km km
v1 = 20 v2 = 120 t = 15 s
hr hr
Solution:
v2 − v1 m
a = a =
t 2
s
1 2
dv= 1 t + at d = m
2
Problem 12-2
A car starts from rest and reaches a speed v after traveling a distance d along a straight road.
Determine its constant acceleration and the time of travel.
ft
Given: v = 80 d = 500 ft
s
Solution:
2
2 v ft
v = 2ad a = a =
2d 2
s
v
vat= t = t = s
a
Problem 12-3
A baseball is thrown downward from a tower of height h with an initial speed v0. Determine
the speed at which it hits the ground and the time of travel.
Given:
ft ft
h = 50 ft g = v0 = 18
2 s
s
Solution:
2 ft
vv= 0 + 2gh v =
s
1
Engineering Mechanics - Dynamics Chapter 12
vv− 0
t = t = s
g
*Problem 12–4
Starting from rest, a particle moving in a straight line has an acceleration of a = (bt + c). What
is the particle’s velocity at t1 and what is its position at t2?
m m
Given: b = 2 c = −6 t1 = 6s t2 = 11 s
3 2
s s
Solution:
⌠t ⌠t
at() = bt+ c vt() = ⎮ at()dt dt() = ⎮ vt()dt
⌡0 ⌡0
m
vt()1 = 0 dt()2 = m
s
Problem 12-5
Traveling with an initial speed v0 a car accelerates at rate a along a straight road. How long will it
take to reach a speed vf ? Also, through what distance does the car travel during this time?
km km km
Given: v0 = 70 a = 6000 vf = 120
hr 2 hr
hr
Solution:
vf − v0
vf = v0 + at t = t = 30 s
a
2 2
2 2 vf − v0
vf = v0 + 2as s = s = 792 m
2a
Problem 12-6
− b t
A freigh